Oil production



Nov. 29, 1955 R, SPEARQW 2,725,106

OIL PRODUCTION Filed Deo. 20, 1951 2 Sheets-Sheet l .v A ,fr l I I i lTTORNEK Nov. 29, 1955 sPl-:ARow 2,725,106

OIL PRODUCTION 2 Sheets-Sheet 2 n .v0.7 0. 7/ V 0,. l N r ZZM N .f w

' INVENTOR.

United Statesl Patent O OIL PRODUCTION Ralph Spearow, Paola, Kans.

Application December 20, 1951, Serial No. 262,568

4 Claims. (Cl. 166-9) This invention relates to improvements in theprocess for producing oil from oil sands and refers more particularly toa process which may be utilized either as a primary oil productionmethod or a secondary oil production method whereby oil is producedfromr an oil producing horizon or reservoir after conventionalproduction methods or processes have become uneconomical.

This application is a continuation in part of a prior application SerialNo. 750,396 filed May 26, 1947, now Patent No. 2,593,497 issued April22, 1952. i

In many of the numerous oil producing areas all over the world there arefields where production is no longer commercially feasible due to thefact that the original pressure in the oil stratum has been exhausted tothe extent that the fluid oil will no longer movethrough the sand intothe wells in sufficient quantities to permit profitable operation. Themere fact thatthese fields are no longer commercially profitable doesnot mean that the oil supply has been depleted, for core samples takenfrom many of these fields after abandonment reveal that more oil remainsthan was removed.

Attempts have been made to improve the initial oil production methodsand numerous secondary recovery methods have been devised to produce oilleft in abandoned fields with varying degrees of success. No secondarymethod yet discovered has been successful in eliminating two principalobjections: First is the fact that the method does not exceedsubstantially the efficiency of the original or primary productionmethod, so there is still left in the reservoir too large a percentageof oil; second, cost of operating the secondary method seldom justiesthe oil recovered.

The instant process diifers from what has preceded in that pressure isapplied to the top of the reservoir to cause the fluid in the sand tomigrate downwardly as a body and recovery of the oil from the reservoiris from its lower regions at or near the bottom.

Fig. 1 is a cross-sectional View taken through the geologic structure ofan oil field showing two wells each of which is both a pressure andproduction well.

Fig. 2 is a cross-sectional view taken through the geologic structure ofan oil field showing three wells, one of which is a pressure well, theother two being production wells.

Referring to Fig. 2, at is indicated the overlying geologic structurewith an impervious layer 11 above the oil sand 12. The structure belowthe oil sand is indicated at 13. The pressure well is drilled from thesurface through the impervious layer 11 into the top of the oil sand,and a casing 14 is run into the Well and is cemented as shown at 15. Thepressure well casing is capped by means of a iianged fitting 16, andconnected into the top of the casing is a pipe 17. Pressure gauge A18 inthe top of the casing indicates pressure on the casing at that point.

The production well or wells are drilled through the oil sand andcasings are run as shown at 19. The pro-l duction well casings arecemented as is the pressure well ICC as indicated at 15. After thecasings in the production wells have been cemented, both the casing andannular cement columns are shot with perforations 20,1ocatcd at or nearthe bottom of the sand 12. The production casings are capped to makethem pressure tight and within the casing is a tubing 21. Oil may beproduced, either by natural flow through the casing 19 or by pumpingthrough tubing 21. Pump rods are indicatedl dia grammatically at 22, thepump being encased in' the tubing at the bottom of the well andmechanism for reciprocating the pump rod at the surface not shown.Discharge pipes 23 controlled by valves 24 are tapped into the casings19 above ground level for removing the oil produced by flowing anddischarge pipes 24 controlled by suitable valves 25 are connected intothe tubing 21 to withdraw oil pumped from the sand through the tubing. n

The location of the pressure and production wells in the field willdepend upon the size and shape of the oil reservoir and to a greatextent will be governed by the engineer or person in charge of producingthe oil. In so far as the process is concerned, it is essential only todrill the pressure wells into the top of the oil sand in locations wherethe air or gas charged to the oil sand will be distributed over theentire area of the field imposing a relatively constant and uniformpressure upon the sand being produced. The number of pressure wellsnecessary will to a great extent depend upon the size of the field andthe rapidity at which the field is to be produced. It is especiallyimportant that the impervious layer 11 above the sand is tightly sealedby the cement columns to the well casings of both the pressure andproduction wells in order to reduce loss of pressure in so far aspossible.

The location of the production wells likewise is a matter of judgmentwith the producer and the geologists in charge of the operations, sincethey should be located advantageouslyr to withdraw the oil from thebottom of the sand as it moves downwardly due to pressure applied on topof the sand by the pressure wells. The number of production wellsnecessary will to a great extent depend upon the size and shape of thefield. The necessity for pumping the wells will of course be determinedby whether the pressure imposed is sufhcient to ow l the wells withoutresorting to mechanical means to raise the oil to the surface.

Pressure may be imposed in the form of gas if available or by air andshould be supplied into the pressure wells through pipe 17. The amountof pressure required will be determined by the necessity ofsupplementing gas pressure already in the sand to drive the oildownwardly through the sand to the production wells. In depleted oilsands Where little or no pressure exists, sufficient pressure must besupplied to force the oil into the production wells where it isaccumulated and pumped to the surface where suflicient pressure isapplied and the sand is at a shallow depth below the surface the wellsmay again flow naturally.

In Fig. l is shown a modification of the method illustrated in Fig. 2.In this figure like numerals are used to refer to like parts of Fig. 2.However, in this modification a packer 26 is employed to seal off thespace between casing 19 and tubing 21 intermediate the top and bottom ofsand 12. The casing 19 and cement column 15 are also shot above thepacker 26 at 20a. Pipe 23a controlled by valve 24a is employed as an airpressure input into the space between casing 19 and tubing 21.

In an actual operation in eastern Kansas where a small shallow field hadbeen abandoned for ten years or more, most of the old wells were pluggedand nine new wells drilled through the producing sand. The old wellswhich were not plugged were cleaned and the casing cemented in themanner described in Fig. l. An inner casing and packer were set in eachof the old wells according to the procedure described and shown inFig. 1. The old wells and the new wells were cemented to seal olf theoil sand from the overlying geologic structure and provided a sealbetween the casings and the impervious layer above the producing sand.

After the wells had been completed, air pressure was applied to the oldwells in which the packers had been placed by eight motor drivencompressors. The pressure at the well heads of the pressure wells was500 pounds per square inch and pressures ranging from 250 to 300 poundsat the well heads of the adjoining producing wells. During the initialstages of operation, the old wells began, within ka matter of hoursafter pressure was built up, to produce water which had accumulated overa period of years in these wells due to the fact that the field wasalong a river bottom which was under Water periodically and for shortperiods almost every year. The new wells drilled in the field neverproduced anything but oil.

From the available records, none of the Wells in this field had everproduced more than nine to ten barrels a day. The two old wells whichwere renovated and operated according to the procedure described inconnection with Fig. l are currently being produced at the rate of 200barrels for a 24-hour day. Some of the more remote wells from thepressure input location are being produced at the rate of from 50 to 75barrels per day.

All of the wells which were drilled under the instant program ofrehabilitation besides being carefully cemented, were perforated nearthe bottom of the sand and and the pressure wells perforated both at thebottom of the sand and at the top of the sand above the packer asindicated in Fig. 1 of the drawing.

It is recognized that in secondary production methods air, gas or waterhave been used to force the oil laterally through the sand from alocation where the air, gas or water pressure is applied to the sand;but difficulties are encountered with these operations because it isalmost impossible to force the oil laterally or horizontally through thesand. Attempts have also been made to bore ducts laterally into theproducing sand from a pressure Well at different levels and introducegas or air from the surface to cause the oil to migrate away from thepressure well into production wells. The objection to this type ofoperation is the difficulty encountered in drilling the lateral ductsinto the oil sand for any distance or to so distribute the ducts in thefield to render them effective for the purpose intended.

The instant method supplies the pressure medium, either air or gas, atthe top of the sand where the sand is most porous and contains the leastamount of uid oil so the gas or air supplied under pressure moves morefreely and spreads laterally through the top of the sand building up apressure space in the upper regions of the sand. Pressure applied inthis manner causes a uniform migration of the fluid oil downwardlythrough the sand causing it to accumulate in the lower regions of thesand from which it may be Withdrawn more eiiicaciously through theproducing wells. By this process the creation of gas or air pockets andthe difliculties of channeling of the air and gas through the lessimpervious or porous regions of the sand is to a great extenteliminated.

From the foregoing it will be seen that the invention is well adapted toattain all lof the ends and objects hereinabove set forth, together withother advantages which are obvious and which are inherent to the methodand apparatus. It will be understood that certain features andsubcombinations are of utility and may be employed without reference toother features and subcornbinations. This is contemplated by and iswithin the scope of the claims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the drawings is to be interpreted asillustrative and not in a limiting sense.

Having thus described my invention, I claim:

1. A method of producing oil from an oil reservoir by a gaseous pressuremedium supplied from the ground level to said reservoir, comprising thesteps of drilling a pressure input well to the top of the reservoir,running a casing in said input well, sealing said casing to thesurrounding formation from the top of the reservoir to a level abovesaid reservoir, drilling a production well to the vicinity of the bottomof said reservoir, running a casing in said production well to thebottom thereof, sealing said last mentioned casing to the surroundingformation from the vicinity of the bottom of said casing to a levelabove the top of the reservoir, applying a gaseous medium under pressurethrough said input Well onto the top of the oil reservoir, said inputwell casing seal being of such strength as to confine such pressures asmay be applied to the top of the reservoir, and said production wellcasing seal being of such strength as to prevent vertical leakage of thepressure medium along the surface of contact of the sealing material andthe surrounding formation whereby a vertical pressure is imposed andmaintained in the reservoir to produce oil from the production well.

2. A method in claim l including the step of perforating the casingadjacent the bottom of the reservoir.

3. A method as in claim 1 wherein a plurality of production wells areused with a single input Well.

4. A method as in claim l wherein a plurality of production Wells areused with a plurality of input wells.

References Cited in the le of this patent UNITED STATES PATENTS1,252,557 Dunn Jan. 8, 1918 l,722,679 Ranney July 30, 1929 .l,8ll,561Ranney June 23, 1931 1,816,260 Lee July 28, 1831 2,188,737 Hixon Ian.30, 1940 2,297,832 Hudson Oct. 6, 1942

1. A METHOD OF PRODUCING OIL FROM RESERVOIR BY A GASEOUS PRESSURE MEDIUMSUPPLIED FROM THE GROUND LEVEL TO SAID RESERVOIR, COMPRISING THE STEPSOF DRILLING A PRESSURE INPUT WELL TO THE TOP OF THE RESERVOIR, RUNNING ACASING IN SAID INPUT WELL, SEALING SAID CASING TO THE SURROUNDINGFORMATION FROM THE TOP OF THE RESERVOIR TO A LEVEL ABOVE SAID RESERVOIR,DRILLING A PRODUCTIUON WELL TO THE VICINITY OF THE BOTTOM OF SAIDRESERVOIR, RUNNING A CASING IN SAID PRODUCTION WELL TO THE BOTTOMTHEREOF, SEALING SAID LAST MENTIONED CASING TO THE SURROUNDING FORMATIONFROM THE VICINITY OF THE BOTTOM OF SAID CASING TO A LEVEL ABOVE THE TOPOF THE RESERVOIR, APPLYING A GASEOUS MEDIUM UNDER PRESSURE THROUGH SAIDINPUT WELL ONTO THE TOP OF THE OIL RESERVOIR, SAID INPUT WELL CASINGSEAL BEING OF SUCH STRENGTH AS TO CONFINE SUCH PRESSURES AS MAY BEAPPLIED TO THE TOP OF THE RESERVOIR, AND SAID PRODUCTION WELL CASINGSEAL BEING OF SUCH STRENGTH AS TO PREVENT VERTICAL LEAKAGE OF THEPRESSURE MEDIUM AND THE THE SURFACE OF CONTACT OF THE SEALING MATERIALAND THE SURROUNDING FORMATION WHEREBY A VERTICAL PRESURE IS IMPOSED ANDMAINTAINED IN THE RESERVOIR TO PRODUCE OIL FROM THE PRODUCTION WELL.